The Ox-Bow Incident (1943)

One of the best westerns not directed by John Ford (who before Clint Eastwood revitalized the genre was God).  The director here is Wlliam A. Wellman and the film is a masterpiece.  It tells how a blood-thirsty mob looking to avenge a killing (which as it turns out didn't occur) form a lynch-mob and hang three innocent men (Dana Andrews, Anthony Quinn, and Francis Ford -- John's brother).  Only seven of their number including Henry Fonda and his side-kick Harry Morgan (Col. Potter from MASH), newly arrived in the town, and the lovely character actor Harry Davenport try to air the voice of reason.  All to no avail, as the vultures have their way.  The film ends with Fonda reading out Andrews' farewell letter to his wife and family, as the culprits look shame-facedly away.  Very moving and no doubt faithful to many such outrages.